This application claims priority under 35 USC xc2xa7119 from Swedish Patent Application No. 0100276-5, filed Jan. 31, 2001.
Field of the Invention
Different kinds of boards and other flat elements which are joined to each other by means of tongue and groove are well known. Tongue and groove are nowadays normally made by milling which is a rational method. It is however difficult to achieve complex cross-sections with undercuts with traditional milling, especially in narrow grooves. It is known to achieve undercuts to some degree by utilising more than one milling tool with different rotation axis. The problem with this method is however that it is very difficult to obtain desirable tolerances due to vibrations and flexing in the machine since there must be some distance between the different milling tools. The cross-section possible to manufacture by this method is also limited since the milling tool will have to rotate through the opening of for example a groove. It is desirable to achieve a process where the tolerance play is good, undercuts with sharper angles are possible to manufacture and where dust and particles form the milling isn""t obstructing the process.
It has, according to the process of the present invention, been made possible to achieve profiles such as tongue and groove on boards, with better tolerances, undercuts with sharper angles and without having dust and particles from the milling process obstructing the process.
Accordingly, the invention relates to a process for the manufacturing of longitudinal profiles such and tongue and groove on boards wherein the process includes the steps;
a) Moulding a substantial part of the profile cross-section by means of milling with a milling tool.
b) Fine moulding undercuts in at least the groove of the board by means of broaching utilising at least one broaching tool.
The milling tool is adjustably fixed in a conveying machine, which machine feeds the boards past the milling tool during the milling operation. The broaching tool is preferably adjustably fixed in the same conveying machine, which machine feeds the board past the broaching tool. The process is most suitably used for machining tongue and groove on thin boards such as floor boards. The tongue and groove may, through the process, be provided with a functionality which allows them to snap join. Accordingly, the moulding of the profiles is initiated by milling a substantial part of the material to be removed with a traditional milling tool. The final shape of the profiles are then achieved by broaching. The undercuts are also achieved in the broaching stage of the process.
If materials like fibre board or particle board are used it is known that burrs often occur which will obstruct the functionality in the tighter parts of a snap joint. This can be avoided by adding the step of coating of the milled profile section before the broaching stage where the fine moulding takes place. The coating suitably comprises a substance such as wax, oil, a polymeric material being exemplified by a thermoplastic polyolefin and a lacquer being exemplified by a UV-curing lacquer.
The broaching tool preferably comprises broaching edges, a broaching body and a broaching clamp. The broaching body is suitably provided with internal cooling channels for a cooling media, the cooling media being selected from the group consisting of a gas and a liquid. The broaching body is suitably also provided with a temperature sensor used for guiding the cooling. The temperature sensor is either an infrared sensor directed towards one or more broaching edges or a conductive sensor attached to the broaching body. The broaching tool is suitably provided with at least one nozzle for blowing air on the broaching edges. The air blown on the broaching edges may serve two purposes the first one being to remove dust and particles from the cutting edges the second one being to cool the broaching tool. It is possible to use the blown air as either a complement to, or a replacement for the internal cooling. The broaching tool is suitably also provided with an air and dust evacuation duct which evacuates dust and particles from the broaching edges. The air blown on the edges may suitably also pulsate for better cleaning of the edges.
The front edge portions of the broaching edges are suitably concave in order to increase the stability during the cutting operation and at the same time ensure secure removal of the waste material so that no or very little burr is formed. The side edge portions of the broaching edges are suitably also concave in order to increase the stability during the cutting operation and at the same time ensure secure removal of the waste material so that no or very little burr is formed.